Model systems for membrane fusion

Membrane fusion has an overarching influence on living organisms. The fusion of sperm and egg membranes initiates the life of a sexually reproducing organism. Intracellular membrane fusion facilitates molecular trafficking within every cell of the organism during its entire lifetime, and virus-cell membrane fusion may signal the end of the organism's life. Considering its importance, surprisingly little is known about the molecular-level mechanism of membrane fusion. Due to the complexity of a living cell, observations often leave room for ambiguity in interpretation. Therefore artificial model systems composed of only a few components are being used to further our understanding of controlled fusion processes. In this critical review we first give an overview of the hypothesized mechanism of membrane fusion and the techniques that are used to investigate it, and then present a selection of non-targeted and targeted model systems, finishing with current applications and predictions on future developments (85 references).     

Flip motion of heterogeneous buckled dimers on Ge(0 0 1) by electron injection from STM tip

Surface motion of a topological defect between p(2×2) and c(4×2) structures, a “kink”, across buckled Sn-Ge and Si-Ge dimers on Ge(0 0 1) surfaces was investigated using scanning tunneling microscopy. Energy thresholds of π^∗ electrons for flipping these dimers in the kink are obtained by analyzing the kink surface motion. Electronic states of these systems and energy barriers for flipping the dimers are examined by first-principles calculations for considering elementary processes of the electronically-excited flip motion of the dimers. We propose that the flip motion is caused by a resonant scattering of the π^∗ electrons with localized electronic states at the kink.     

Synthesis and evaluation of N-phenyl-(2-aminothiazol-4-yl)acetamides with phenoxypropanolamine moiety as selective β3-adrenergic receptor agonists

In the search for potent and selective human β3-adrenergic receptor (AR) agonists as potential drugs for use in treating obesity and non-insulin dependent (type 2) diabetes, a series of N-phenyl-(2-aminothiazol-4-yl)acetamides with phenoxypropanolamine moiety were prepared and their biological activities against human β3-, β2-, and β1-ARs were evaluated. Among these compounds, N-phenyl-(2-phenylaminothiazol-4-yl)acetamide (4 g), N-phenyl-(2-benzylaminothiazol-4-yl)acetamide (4j), and N-phenyl-[2-(3-methoxyphenyl)aminothiazol-4-yl]acetamide (6g) derivatives showed potent agonistic activity against the β3-AR with functional selectivity over the β1- and β2-ARs. In addition, these compounds exhibited significant hypoglycemic activity in a rodent model of diabetes.     

Non-contact acoustic tests based on nanosecond laser ablation: Generation of a pulse sound source with a small amplitude

A method to generate a pulse sound source for acoustic tests based on nanosecond laser ablation with a plasma plume is discussed. Irradiating a solid surface with a laser beam expands a high-temperature plasma plume composed of free electrons, ionized atoms, etc. at a high velocity throughout ambient air. The shockwave generated by the plasma plume becomes the pulse sound source. A laser ablation sound source has two features. Because laser ablation is induced when the laser fluence reaches 10¹²–10¹⁴ W/m², which is less than that for laser-induced breakdown (10¹⁵ W/m²), laser ablation can generate a lower sound pressure, and the sound source has a hemispherical radiation pattern on the surface where laser ablation is generated. Additionally, another feature is that laser-induced breakdown sound sources can fluctuate, whereas laser ablation sound sources do not because laser ablation is produced at a laser beam–irradiation point. We validate this laser ablation method for acoustic tests by comparing the measured and theoretical resonant frequencies of an impedance tube.     

Vibration testing based on impulse response excited by laser ablation

This paper proposes an innovative vibration testing method based on impulse response excited by laser ablation. In conventional vibration testing using an impulse hammer, high-frequency elements of over tens of kilohertz are barely present in the excitation force. A pulsed high-power YAG laser is used in this study for producing an ideal impulse force on a structural surface. Illuminating a point on a metal with the well-focused YAG laser, laser ablation is caused by generation of plasma on the metal. As a result, an ideal impulse excitation force generated by laser ablation is applied to the point on the structure. Therefore, it is possible to measure high-frequency FRFs due to the laser excitation. A water droplet overlay on the metal is used to adjust the force magnitude of laser excitation. An aluminum block that has nine natural frequencies below 40 kHz is employed as a test piece. The validity of the proposed method is verified by comparing the FRFs of the block obtained by the laser excitation, impulse hammer, and finite element analysis. Furthermore, the relationship between accuracy of FRF measurements and sensitivity of sensors is investigated.     

Frequency measurement of pure rotational transitions in the v2 = 1 state of H2O

Frequencies of pure rotational transitions in the v₂ = 1 vibrationally excited state of H₂¹⁶O were measured with a tunable far-infrared spectrometer in the frequency range of 0.5-5 THz. Molecular parameters of Watson’s A-reduced Hamiltonian have been obtained to reproduce the observed frequencies.     

Compact quantum ergodic systems

We develop theory of multiplicity maps for compact quantum groups. As an application, we obtain a complete classification of right coideal C^∗-algebras of C(SUq(2)) for q∈[−1,1)?{0}. They are labeled with Dynkin diagrams, but classification results for positive and negative cases of q are different. Many of the coideals are quantum spheres or quotient spaces by quantum subgroups, but we do have other ones in our classification list.     

Chemical analysis of surface hydrocarbons in fireflies by direct contact extraction and gas chromatography-mass spectrometry.

We characterized three Japanese firefly species (Luciola lateralis, Luciola cruciata, and Lucidina biplagiata) and three North American firefly species (Lucidota atra, Photuris lucicrescens, and Photuris cinctipennis) based on their surface hydrocarbons. The analysis of firefly extracts by gas chromatography-mass spectrometry (GC-MS) revealed clear differences in the chromatographic profiles and mass spectra. Each firefly could be distinguished by its GC-MS profile. A major difference was observed between Japanese fireflies and North American fireflies. Among the North American fireflies, non-luminous fireflies, Lucidota atra, showed much more complicated GC-MS profile than those of luminous fireflies, Photuris lucicrescens and Photuris cinctipennis.     

Classification of minimal actions of a compact Kac algebra with amenable dual on injective factors of type III

We classify a certain class of minimal actions of a compact Kac algebra with amenable dual on injective factors of type III. The structural analysis of type III factors and the canonical extension of endomorphisms introduced by Izumi are our main technical tools.